Extended discharge systems for electrostatic precipitators



R E I wQ iU l n I QW I I I I I I I T I I MU N Z N I I I I I I I I I I I I I I I l I I J E I III I. m m 6 2. w 7/ 3 3 2 m c Z n A N M IN A I id/Ni i I I n I I I H I I I v T m I I I I I I I I I I I I I I I I I I I I I I I M July. 7, 1970 I H. c. WERNER EXTENDED DISCHARGE SYSTEMS FOR ELECTROSTATIC PRECIPITATOPS Filed Sept. 4. 1968 United States Patent O 3,518,813 EXTENDED DISCHARGE SYSTEMS FOR ELECTROSTATIC PRECIPITATORS Hermann C. Werner, Ridgewood, NJL, assignor to Airetron Engineering Corporation, 'Midland Park, N.J., a corporation of New Jersey Filed Sept. 4, 1968, Ser. No. 757,293 Int. Cl. B03c 3/08 US. Cl. 55-136 7 Claims ABSTRACT OF THE DISCLOSURE An extended discharge system for electrostatic precipitators including further discharge electrodes disposed downstream from the main electrostatic precipitator stack and further collection plates spaced downstream from said further discharge electrodes and adapted to receive and retain precipitant while permitting the continued flow thereby of the fluid from which the precipitant is being removed. The further discharge electrodes are preferably adapted to produce a directional electrostatic field extending substantially in the direction of flow of said fluid.

BACKGROUND OF THE INVENTION This invention relates generally to electrostatic precipitators of the type wherein a plurality of discharge electrodes are interposed between a plurality of spaced collection plates. Such electrostatic precipitators are used for air pollution control, gas cleaning, separation and selective particle removal. Generally, the fluid containing the material to be precipitated flows, under positive or negative pressure, between the collection plates and past the discharge electrodes which are adapted to produce a corona and electrostatic field when a sufficiently high voltage is applied thereto. The voltage is preferably negative to produce a negative corona effect and ionization.

Both positive and negative ions are generated in the corona, the positive ions remaining on the negativelycharged discharge electrode, while the negative ions pass over to the grounded collection plate along the lines of force of the electrostatic field which extends therebetween. The particles to be precipitated intercept the negative ions, are charged thereby, and are attracted to the adjacent collection plate. The collection plates are generally provided with baflles, or other means to prevent the precipitant from being reentrained in the fluid due to the passage of the fluid past the collection plates. The fluid leaving the electrostatic precipitator moves on to recovery or exhaust.

Although electrostatic precipitators of the foregoing description are highly efiicient, a minute amount of charged and neutral particles generally escapes from the downstream side of the stack of alternating collection plates and discharge electrodes. Such particles, either never reached the collection plates or were reentrained therefrom by the fluid passing thereby. These particles move with the fluid and experience has shown that the charged particles partially attached themselves to pipes and walls downstream of the collection plate area. By adding an extended discharge system combined with an additional dust collecting device downstream of the main electrostatic precipitator stack, the foregoing can be utilized for improvement of the electrostatic dust removal.

SUMMARY OF THE INVENTION Generally speaking, in accordance with the invention, an extended discharge system for electrostatic precipitators of the type wherein a plurality of discharge electrodes are interposed between a plurality of spaced col- "ice lector plates is provided. The extended discharge system includes a plurality of further discharge electrodes disposed downstream of said first-mentioned discharge electrodes in the path of the fluid from which material is to be precipitated, and a plurality of further collection plates spaced downsteram of said further discharge electrodes in the path of said fluid, said further collection plates being adapted to receive and retain precipitated material while permitting the continued flow of the fluid. The further discharge electrodes are adapted to produce a directional electrostatic field extending substantially in the direction of flow of the fluid and are formed with a plurality of sharp edges or points on the side thereof facing in the direction of the flow of said fluid while being substantially free from sharp edges or points on the other sides thereof. The further discharge electrodes are coupled to and supported by the frame supporting the main discharge electrodes, said coupling being conduc' tive so that the main discharge electrodes and further discharge electrodes are electrically connected.

Accordingly, it is an object of this invention to provide an extended discharge system for electrostatic precipitators.

Another object of the invention is to increase the efficiency of electrostatic precipitators.

A further object of the invention is to provide an electrostatic precipitator where substantially all of the precipitant is collected by the various collection plates, so that the number of escaping particles is substantially lessened.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understand ng of the invention, reference is bad to the following descripion taken in connection with the accompanying drawing, in which:

FIG. 1 is a perspective view of a stack of alternating collection plates and frames carrying discharge electrodes. with portions broken away, in combination with an extended discharge system according to the invention;

FIG. 2 is a partial enlarged sectional view taken along lines 22 of FIG. 1;

FIG. 3 is a partial enlarged sectional view taken along lines 3--3 of FIG. 1; and

FIG. 4 is a cross-sectional view of an alternate embodiment of the further collection plates according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing, the electrostatic precipitator shown includes a stack 10 consisting of alternating collection plates 12 and frames 14 carrying discharge electrodes 16, and the extended discharge system 18 according to the invention.

The construction and operation of stack 10 is well known in the prior art. In one example of the construction thereof, as shown in the drawing. the collection plates 12 are equally spaced from each other in substantially parallel relation. Centrally disposed between collection plates 12 are frames 14 which are preferably formed from a plurality of lengths of pipe. Each frame consists of a top section 20, a bottom section 22 and side sections 24 and 26. Extending between top and bottom sections 20 and 22 and secured thereto are discharge electrodes 16. The discharge electrodes shown are in the form of a plurality of spaced thin wire conductors. If desired, the wire conductors may be formed with sharp edges (star wire) or with spaced points extending therefrom to enhance the corona effect. Secured to the top section 20 of each frame are supports 28 formed from an electrically conducting material. Fixed to each support 28 is an insulator 30 adapted to be extend through and secured against the casing (not shown) of the electrostatic precipitator so that the frames 14 may be supported on said casing while being electrically insulated therefrom. Supports 28 are connected to a source of high voltage (not shown) whereby the operative voltage may be provided to the discharge electrodes 16 for the production of an electrostatic field and corona thereat.

A plurality of spaced channel-shaped members 32 are secured to collection plates 12. The outwardly curved walls 34 of members 32 extend into the space between adjacent collection plates and define between said members substantially turbulence free sections 36. The members 32 extend substantially parallel to discharge electrodes 16 and are disposed on the collection plates so that at least one of said discharge electrodes faces each of said turbulence free sections. Collection plates 12 are preferably grounded.

In operation, the fluid, preferably a gas, containing the material to be precipitated flows in the direction of arrows 38 through stack 10. The fluid flows between the spaced collection plates 12 past discharge electrodes 16. Due to the action of the corona formed at discharge electrodes 16 and the electrostatic field extending between said discharge electrodes and collection plates, the precipitant collects in turbulence free sections 36 at collection plates 12.

The foregoing detailed description of stack is given by way of example and not by way of limitation. Collection plates 12, frames 14 and discharge electrodes 16 may be of any desired design and configuration. Thus, the discharge electrode 16 may be disposed and formed as taught in my copending application Ser. No. 757,292, filed Sept. 4, 1968, entitled Electrostatic Precipitators and assigned to the assignee herein. The wire discharge electrodes may be stabilized by means of weights secured to their lower ends rather than by being secured to bottom section 22 of frame 14 as shown in the drawing. In addition, various means may be incorporated in collection plates 12 for retaining the precipitant collected thereon.

The extended discharge system 18 according to the invention is disposed at the downstream side 39 of stack 10. Extended discharge system 18 consists of further discharge electrodes 40 spaced downstream from frame 14 and further collection plates 42 spaced downstream from said further discharge electrodes. Each discharge electrode 40 is formed with a plurality of spaced sharp points 44 extending therefrom on the side thereof facing in the direction of the flow of the fluid. These points 44 are adapted to produce a corona elfect and a substantially directional electrostatic field extending in the direction of the flow of said fluid. Each of said further discharge electrodes 40 is supported by and electrically connected to side 26 of one of frames 14 by means of coupling members 46. In this manner, the voltage applied through supports 28 is applied not only to discharge electrodes 16 but also to further discharge electrodes 40, so that separate support and electrical distribution system is not required for the extended discharge system 18. However, separate supports and connections to the voltage supply may be provided if desired.

In the embodiment shown in the drawing, coupling members 46 and discharge electrodes 40 are formed from lengths of pipe, points 44 being secured to one side of the further discharge electrodes. However, further discharge electrodes 40 need not be formed from lengths of pipe, but could be formed from a bar of metal or the like. In addition, the further discharge electrodes according to the invention are not limited to electrodes having sharp points 42 extending therefrom. A substantially directional corona effect may also be produced by sharp edges formed, for example, by cutting spaced notches on the side of further discharge electrodes 40 facing in the direction of flow of the fluid or by securing sharp ridges to said further discharge electrode side.

Further collection plates 42 are adapted to receive and retain such of the material to be precipitated as might have escaped the collection plates 12 of stack 10, without obstructing the continued flow of the fluid. The further collection plates, as shown in FIGS. 1 and 3, are V- shaped and include pockets 48 wherein the precipitant is retained. The spacing between the individual further collection plates permits the continued flow of the fluid thereby and out of the electrostatic precipitator.

A second embodiment of the further collection plates according to the invention is shown in FIG. 4 wherein each of said further collection plates 50 are of a substantially fishhook shape. Each further collection plate 50 is also provided with a pocket 52 defined by a portion thereof 54 extending normally to the direction of flow of the fluid. Said fluid would flow in the direction of arrows 56. The further collection plates may be of any geometric shape provided they are adapted to receive and retain the precipitated material while permitting the continued flow of the fluid thereby. The further collection plates are preferably grounded.

Further discharge electrodes 40 are preferably disposed spaced from and parallel to frames 14 and equidistant from adjacent collection plates 12. In this position, they are in the path of the fluid discharged from the spaces between adjacent collection plates 12. The further collection plates 42 are disposed in staggered lines so as to be in the path of substantially all of the fluid without obstructing its continued flow. Said further discharge electrodes are preferably disposed so that the pocket 48 or 52 of at least one of said further collection plates is disposed facing each of said further discharge electrodes and the sharp points 44 extending therefrom. Electrostatic precipitators frequently consist of several stages, each stage being similar in construction to stack 10. The extended discharge system according to the invention may be interposed between the various stages as well as being placed downstream of the last stage.

The extended discharge system 18 according to the invention is specifically adapted to collect the small percentages of material to be precipitated which escapes from conventional electrostatic precipitators as represented by stack 10. Particles of such material are generally charged to some extent. The extended discharge system 18 according to the invention further charges such particles and collects them at further collection plates 42, thereby increasing the efiiciency of the entire electrostatic precipitator. By designing the further discharge electrodes 40 to produce a substantially directional electrostatic field extending in the direction of flow of the fluid, any particles remaining in the fluid are specifically directed to further collection plates 42. On the other hand, were the extended discharge electrodes adapted to produce an electrostatic field extending in all directions, as would be the case if they were formed from thin wire conductors, a larger portion of the particles might be directed toward and adhere to the side walls of the electrostatic precipitator casing since said further discharge electrodes are preferably disposed beyond the downstream side 39 of collection plates 12.

It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efliciently attained and, since certain changes may be made in the above construction without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawing will be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. In combination with an electrostatic precipitator for the precipitation of materials from fluid having a plurality of first discharge electrodes interposed in the regions be tween a plurality of spaced first collection plates, said first collection plates having an inlet side for the entry of said fluid and an outlet side spaced from said inlet side for the discharge of said fluid, said fluid flowing from said inlet to said outlet side between said collection plates past said first discharge electrodes, the improvement which comprises, a plurality of second collection plates spaced downstream from said first collection plates outlet side in the path of said fluid, said second collection plates being spaced from each other to permit the passage of said fluid thereby, each of said second collection plates including a portion extending transversely to said first collection plates outlet side and to the direction of flow of said fluid for retaining said precipitant; and second discharge electrodes interposed intermediate said first collection plates outlet side and said second collection plates in the path of said fluid.

2. An electrostatic precipitator as recited in claim 1, wherein the spaces between adjacent first collection plates define fluid passageways terminating in outlets at said outlet side of said first collection plates, said second discharge electrodes being formed of longitudinally extending bars having sharp edges or points formed on the side thereof facing said transverse portions of said second collection plates, at least one of said discharge electrode bars being disposed adjacent to and extending substantially parallel to the outlet of each of said fluid passageways.

3. An electrostatic precipitator as recited in claim 1, wherein said first and second discharge electrodes are maintained at substantially the same voltage.

4. An electrostatic precipitator as recited in claim 1, including a plurality of supports interposed between said first collection plates for supporting said first discharge electrodes; and a plurality of coupling members extending between said second discharge electrodes and said supports for supporting said second discharge electrodes, said supports and coupling members being formed from electrically conducting material for the common energization of said first and second discharge electrodes.

5. An electrostatic precipitator as recited in claim 1, wherein said second discharge electrodes are formed with a plurality of sharp edges or points on the side thereof facing said second collection plates.

6. An electrostatic precipitator as recited in claim 5, wherein the other sides of said second discharge electrodes are substantially free from sharp edges or points.

7. An electrostatic precipitator for the precipitation of materials from fluids comprising a plurality of first spaced collection plates disposed in parallel overlapping relation, said first collection plates having an inlet side for the entry of said fluid and an outlet side spaced from said inlet side for the discharge of said fluid; a tubular frame member interposed between each adjacent pair of said first collection plates; a plurality of first discharge electrodes mounted on said frame members in the space between said first collection plates, said fluid flowing from said inlet side to said outlet side between said first collection plates past said first discharge electrodes; a plurality of coupling means mounted on the side of said frame members adjacent said first collection plates outlet side, said coupling members projecting beyond said first collection plates outlet side; a plurality of second collection plates spaced downstream from said first collection plates outlet side in the path of said fluid, said second collection plates being spaced from each other to permit the passage of said fluid thereby, each of said second collection plates including a pocket-shaped portion extending transversely to said first collection plates outlet side, said pocket-shaped portions having the entrances thereof facing said first collection plates outlet side for retaining said precipitant; and second longitudinally extending discharge electrodes mounted on said coupling means intermediate said first collection plates outlet side and said second collection plates, at least one of said second discharge electrodes being adjacent to and extending parallel to the space between each adjacent pair of second collection plates, said second discharge electrodes being formed with sharp edges or points on the side thereof facing said second collection plates.

References Cited UNITED STATES PATENTS 804,291 11/1905 Wood 150X 2,199,390 5/1940 Anderson 55-138 X 2,382,254 8/1945 Penney et al 55137 2,867,285 1/1959 Wintermute 5513 6 X FOREIGN PATENTS 858,837 12/1952 Germany.

19,733 1913 Great Britain. 627,068 7/ 1949 Great Britain. 577,432 5/1958 Italy.

OTHER REFERENCES German printed application No. 1,078,096, printed March 1960.

DENNIS E. TALBERT, IR., Primary Examiner US. Cl. X.R. 

